1. Field of the Invention
The present invention relates to an electronic musical instrument which is capable of preventing an overflow in the addition of waveforms for creating a composite musical waveform.
2. Description of the Prior Art
In the case where two waveforms, such as shown in FIGS. 5A and 5B, are simply added together by conventional digital musical waveform generating means, such a distorted waveform as depicted in FIG. 5C may sometimes be provided.
This is caused by the disappearance of a carry bit to be included in the addition, due to an overflow, and the spectrum of the resulting waveform includes, in addition to spectral components of the waveforms shown in FIGS. 5A and 5B, a noise-like high-frequency component resulting from the deformation of the waveform by the overflow.
Sometimes the noise component is so large that the sound of the composite waveform is quite different from the sound of original waveforms, and the sound of a waveform in which an overflow is present as shown in FIG. 5C can no longer be called a musical sound but it is nothing less than a noise. To avoid the generation of such an overflow, it is necessary to lower the levels of the waveforms of FIGS. 5A and 5B before they are added together. Where the number of waveforms to be added together is large, their levels must be reduced in proportion to the number of waveforms involved. This will narrow the dynamic range of each of the waveforms to be added, resulting in the degradation of the quality of sound.